In the modern information age, both professional and amateur athletes are increasingly interested in quantifying their performance. Various existing devices such as GPS-enabled watches or microchips implanted in shoes measure stride, distance traveled, pace, and other aspects of a user's performance. Other devices measure physiological aspects of a user's performance, such as heart rate. Conventional systems for gathering user performance data, however, are often inconvenient, cumbersome, or difficult to implement. For example, heart rate monitors provide a user with heart rate information, but the user must endure the inconvenience and discomfort of wearing a chest strap and monitoring device.